JP2001247925A - High ductility magnesium alloy excellent in fluidity and magnesium alloy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high ductility magnesium alloy excellent in fluidity and capable of producing a thin product having a large projection are in high pressure casing. SOLUTION: This magnesium alloy has a composition containing 5.0 to 7.0% Al, 0.5 to 1.5% Si, 0.1 to 1.0% Mn and <0.5 Zn at request, and the balance Mg with inevitable impurities. Its fluidity can remarkably be improve without causing casting cracks and deteriorating the mechanical properties thereof, so that a magnesium alloy material large in a projected area can efficiently be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a highly ductile magnesium alloy having excellent fluidity and suitable for various high-pressure casting methods such as metal injection molding, die casting, and squeeze casting, and is manufactured by semi-molten injection molding using the alloy. High ductility magnesium alloy material.

[0002]

2. Description of the Related Art Magnesium alloys are light in weight and have high strength. Conventionally, when manufacturing these members, various high-pressure casting methods such as metal injection molding, die casting, and squeeze casting have been widely adopted. Conventionally, the following Mg-Al alloys have been standardized as magnesium alloys that can be cast at high pressure. In addition, all the following numerical values have mass% as a unit. (1) General-purpose alloy 9Al-0.6Zn-0.3Mn-residual Mg (AZ91D) (2) High ductility alloy 6Al-0.3Mn-residual Mg (AM60B) (3) High ductility alloy 5Al-0.3Mn-residual Mg (AM50A) (4) High ductility alloy 2Al-0.3Mn-residual Mg (AM20) (5) Heat-resistant alloy 4Al-1Si-0.4Mn-Residual Mg (AS41B) (6) Heat-resistant alloy 2Al-1Si- 0.2Zn-0.4Mn-residual Mg (AS21) (7) Heat resistant alloy 4Al-2Mm-0.3Mn-residual Mg (AE42) These magnesium alloys have relatively high strength and In the casting method, it shows good flow of molten metal and has excellent fluidity. In particular, among conventional alloys, AM-based alloys such as AM60B have high ductility in addition to the above properties, and are mainly used as energy absorbing materials in the automotive field, such as a steering wheel core and a seat frame. Have been.

[0003]

However, as in the case of an instrument panel for an automobile, the thickness is small (for example, 2 mm).
If the projected area of the product becomes large with the following thickness),
There is a problem that the fluidity of the molten metal during casting becomes a problem, surface defects due to poor flow of the molten metal easily occur, and the yield of the product is deteriorated. In addition, there is also a problem that the actual strength of the product is reduced due to the defect. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly ductile magnesium alloy that has a further improved fluidity as compared with conventional materials and is applicable to manufacture of a product having a large projected area. .
Still another object is to provide a high-ductility magnesium alloy material manufactured by injection molding using the alloy.

[0004]

Means for Solving the Problems In order to solve the above problems, among the high ductility magnesium alloys having excellent fluidity according to the present invention, the first invention is based on a mass ratio of Al: 5.0 to 7.0.
%, Si: 0.5 to 1.5%, Mn: 0.1 to 1.0%
And the balance consists of Mg and unavoidable impurities.

The highly ductile magnesium alloy having excellent fluidity according to the second aspect of the present invention has a mass ratio of Al: 5.0-7.0%,
i: 0.5 to 1.5%, Mn: 0.1 to 1.0%, Z
n: less than 0.5%, with the balance being Mg and unavoidable impurities. The high ductility magnesium alloy having excellent fluidity according to the third aspect of the present invention is the same as the magnesium alloy according to the first or second aspect, except that the mass ratio of C
a, Sr, Ba, one or more of Mm in total amount;
It is characterized by containing 10 ppm to 0.1%.

A magnesium alloy material according to a fourth aspect of the present invention comprises
The magnesium alloy according to any one of the third to third aspects of the invention is obtained by injection molding in which the magnesium alloy is injected into a mold in a semi-molten state with a solid fraction of 50% or less.

The function of the magnesium alloy component of the present invention and the reason for limiting the content will be described below. Al: 5.0 to 7.0% Al lowers the melting point and the solidus temperature, increases the latent heat, and improves the fluidity. In addition, since it hardly dissolves in the Mg matrix and is concentrated on the solidified front surface of the Mg primary crystal, good fluidity is maintained until a eutectic compound with Mg is formed during solidification. If the Al content is less than 5.0%, sufficient fluidity cannot be obtained, while 7.0%
If it is contained in excess of Mg, Mg ₁₇ Al ₁₂ which is a brittle intermetallic compound having high hardness is crystallized in a large amount, so that ductility is reduced. In particular, when used as an energy absorbing material, the energy absorbing ability becomes insufficient. For these reasons, the content of Al is determined within the above range. In addition, the lower limit is set to 5.
It is desirable to set the upper limit to 2% and the upper limit to 6.8%.

Si: 0.5-1.5% Si forms an intermetallic compound Mg ₂ Si with Mg, and also causes a eutectic reaction with Al to form eutectic Si. . All of these contribute to an increase in latent heat and improve fluidity. In order to obtain the above effect, 0.5% or more of S
i content is required. On the other hand, if the content exceeds 1.5%, eutectic Si having high hardness and brittleness is crystallized in a large amount, and the ductility is extremely reduced. Therefore, the Si content is set to the above range. Further, the content of Si is 0.7% or more, more preferably 1.
When the content is 0% or more, in addition to the above effects, the mechanical properties at the time of low-temperature molding are improved, and molding at a lower temperature (for example, 880K or less) is enabled. For the same reason as above, it is desirable to set the upper limit of Si to 1.4%.

Mn: 0.1 to 1.0% Mn combines with Al to form an intermetallic compound, and suppresses the deterioration of corrosion resistance by forming a solid solution of Fe which is an impurity element. In order to obtain this effect sufficiently, 0.1% or more of M
n is required, and if the content is less than 0.1%, the effect is insufficient. On the other hand, if the content of Mn exceeds 1.0%, the dissolution yield deteriorates, so the Mn content is set in the above range. For the same reason, the lower limit is 0.2% and the upper limit is 0.9%.
% Is desirable.

Zn: less than 0.5% Zn lowers the melting point and can be contained as desired. However, if it is contained more than 0.5%, casting cracks are likely to occur. Less than Note that it is desirable to set the upper limit to 0.4% for the same reason.

Ca, Sr, Ba, Mm: 10 ppm or more
0.1% These elements have an action of suppressing the oxidation of the molten metal while maintaining high fluidity, and are useful for preventing combustion. Therefore, one or more of these elements are contained as required. In order to obtain this effect sufficiently, a total content of 10 ppm or more is necessary.
If the content is less than 3, the flame retardant effect is not sufficient. On the other hand, if the total content exceeds 0.1%, not only is the yield of the molten metal in the molten metal lowered and wasteful, but also there is a problem that cracks are likely to occur during casting. Determine the total amount in the above range. For the same reason, it is desirable to set the lower limit to 30 ppm and the upper limit to 800 ppm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesium alloy of the present invention is smelted with the above component ranges as target values, but the smelting method is not particularly limited as the present invention. Can be adopted. The molten magnesium alloy can be used as a molten metal or once as a slab, and then subjected to a casting process as a subsequent process. In addition, depending on the casting method, the alloy is processed into powder or the like as necessary. As the casting method in the casting process, various generally known methods can be adopted.However, since the magnesium alloy of the present invention has excellent castability, the demand for castability is high, but high quality is required. It is a material suitable for high-pressure casting such as die casting, squeeze casting, and injection molding from which a material can be obtained. The conditions of these casting methods are not particularly limited as the present invention, but in semi-solid injection molding, it is desirable that the solid phase ratio of the molten metal be 50% or less. This is because if the solid phase ratio exceeds 50%, even with the alloy of the present invention having good castability, the fluidity of the molten metal may be low, and good injection molding may be difficult.

In the above-mentioned high-pressure casting method, the molten alloy (including the case of semi-molten) has high fluidity, so that it can be cast with good flow even when forming into a product having a large projected area.
High product yield is obtained. In addition, the obtained member has high ductility, and has a small number of surface defects due to a good flow of molten metal, and the actual strength of the product is improved. Therefore, a molded article made of the alloy of the present invention can be used as a lightweight and highly ductile member in various applications, and can be applied to a thin product or a product having a large projected area. Can be manufactured with good yield. Further, by being used in automobiles as a lightweight member, it is possible to improve fuel efficiency and contribute to suppressing global warming. In addition, it is expected to be used for light-weight members requiring strength, such as electric tools and leisure goods. Moreover, these magnesium alloy products are more recyclable than conventional plastic products, and can contribute to the preservation of the global environment.

[0014]

Embodiments of the present invention will be described below. In the components shown in Table 1, the magnesium alloy of the present invention (inventive material), the alloy outside the scope of the present invention for comparison, and the conventional alloy (AM6)
OB) were melted. Although not shown in Table 1, it was confirmed that a large amount of crystallized substances remained in the furnace when a raw material having a Si content of more than 1.5% was used.

[0015]

[Table 1]

The ingot obtained as described above was cut into a raw material chip (approximately 2 mm in size), and was subjected to a metal injection molding method (a clamping force of 450 t), which is one of high pressure casting methods. In this molding, a spiral mold for evaluating fluidity (not shown) was prepared to obtain a spiral molded body 1 having a shape (thickness 2 mm, width 156 mm) shown in FIG. An elongated hole-shaped mold (not shown) was prepared to obtain a tensile test piece 2. Next, in order to evaluate the fluidity, semi-melt injection molding (solid phase ratio of 50% or less) was carried out at the following cylinder temperature and injection speed using the above-mentioned spiral mold for fluidity evaluation. In the evaluation of the fluidity, as shown in FIG. 1, the distance that the molten metal reached the farthest was L2 regardless of the presence or absence of the filling notch, and the complete spiral without the filling notch was found, as shown in FIG. When the reaching distance was L1, L1 was used as the filling flow length in the evaluation.

FIG. 2 is a graph showing a change in filling flow length when injection molding is performed by changing a cylinder temperature and an injection speed in a conventional alloy (AM60B). Was evaluated. As can be seen from this figure, an increase in cylinder temperature improves fluidity, but the difference in fluidity decreases as the injection speed increases.

Next, the influence of the Si content on the fluidity was investigated by injection molding using raw material chips having different Si contents. Specifically, set the cylinder temperature to 8
The material was molded at a constant 88 K while changing the injection speed using each raw material, and the filling flow length at that time was measured. The results are as shown in FIG. 3, where the flow length increases almost linearly with an increase in the Si content, and higher flowability is obtained by using the raw material chips of the present invention. .

Next, in order to investigate the effect of the Si content on the mechanical properties at room temperature, the cylinder temperature and the injection speed were changed, and each raw material chip having a different Si content was used.
Injection molding was performed to obtain a tensile test piece 2. The yield strength, tensile strength and elongation at break of the obtained test piece 2 were measured, and the results are shown in FIGS. 4 shows the proof stress, FIG. 5 shows the tensile strength, and FIG. 6 shows the elongation at break.

As is apparent from FIG. 4, the higher the Si content, the higher the proof stress. The higher the proof stress, the higher the yield strength when the material chip of the present invention is used. On the other hand, as shown in FIGS. 5 and 6, the tensile strength and the elongation at break tend to decrease due to the addition of Si (０．６0.66%), but the difference is within an allowable range. However,
When a raw material containing 1.15% of Si is used, these characteristics are equivalent to those without Si added. In addition, in the case of molding at a low temperature, when a raw material containing no Si and a small amount of Si (up to 0.66%) is used, the tensile strength and the breaking elongation are sharper than when molding at a higher temperature. However, in the case of using a raw material containing 1.15% of Si, there is almost no decrease even in low-temperature molding, and a molded article having excellent mechanical properties can be obtained even in low-temperature molding. it can. From these viewpoints, the content of Si is preferably 0.7% or more, and more preferably 1.0% or more.

From the above results, in the above embodiment, optimally, when a raw material containing 1.15% of Si is used,
It can be seen that a magnesium alloy material having excellent fluidity at the time of casting and having excellent strength and ductility can be obtained. Although not shown in the table, when injection molding was similarly performed using a Zn-containing raw material, 0.5% or more of Zn was
Casting cracks were likely to occur due to the inclusion. In the above embodiment, data relating to the metal injection molding method is shown, but it is a matter of course that the alloy of the present invention can be applied to other high pressure casting methods such as die casting and squeeze.

[0022]

As described above, according to the highly ductile magnesium alloy having excellent fluidity of the present invention, the mass ratio of A
l: 5.0 to 7.0%, Si: 0.5 to 1.5%, M
n: 0.1 to 1.0%, and if desired, Z
n: contains less than 0.5%, and the balance consists of Mg and unavoidable impurities, so that fluidity can be remarkably improved without impairing mechanical properties such as ductility, and light weight having a large projected area The member can also be efficiently manufactured with good yield, and the obtained molded article has excellent mechanical properties. Further, the magnesium alloy material of the present invention has good mechanical properties because it is obtained by injection molding in which the above alloy is injected into a mold in a semi-molten state with a solid fraction of 50% or less. Is also easy.

[Brief description of the drawings]

FIG. 1 is a plan view showing a molded article and a test piece used in Examples.

FIG. 2 is a graph showing the relationship between cylinder temperature and molten metal flow length in a conventional alloy.

FIG. 3 is a graph showing a relationship between a Si content in a raw material and a flow length of a molten metal.

FIG. 4 is a graph showing a relationship between a cylinder temperature and a proof stress when each raw material is used.

FIG. 5 is a graph showing the relationship between cylinder temperature and tensile strength when each raw material is used.

FIG. 6 is a graph showing the relationship between cylinder temperature and elongation when each raw material is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spiral molded object 2 Tensile test piece

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiko Naribe, Inventor 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (72) Ryohei Uchida 1-chome, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima No. 6 in the Japan Steel Works, Ltd.

Claims (4)

[Claims] 1. A mass ratio of Al: 5.0 to 7.0%, S
High ductility magnesium alloy excellent in fluidity, characterized by containing i: 0.5 to 1.5% and Mn: 0.1 to 1.0%, with the balance being Mg and unavoidable impurities. 2. Al: 5.0 to 7.0% by mass ratio, S
i: 0.5 to 1.5%, Mn: 0.1 to 1.0%, Z
n: less than 0.5%, the balance being Mg and unavoidable impurities, characterized by having excellent fluidity and high ductility. 3. The mass ratio of Ca, Sr, Ba,
The highly ductile magnesium alloy having excellent fluidity according to claim 1 or 2, wherein one or more kinds of Mm (mish metal) are contained in a total amount of 10 ppm to 0.1%. 4. A magnesium alloy material obtained by injection molding in which the alloy according to claim 1 is injected into a mold in a semi-molten state having a solid fraction of 50% or less.